The present invention relates to devices, systems, and methods in connection with posterior spinal fusion.
Pedicle screw fixation constructs have been in use for decades in conjunction with spinal fusion procedures, in which adjacent vertebral segments are fused to improve spinal stability or correct certain spinal deformities. Older approaches for inserting these pedicle screw fixation constructs involved open procedures, in which relatively large skin incisions were created to expose a substantial portion of the patient's spinal column, in order to allow for insertion of the pedicle screws and manipulation of spinal rods through openings adjacent to the heads of the screws.
Over time, less invasive approaches have been developed. Typically, in such approaches, pedicle screws are inserted into the pedicles of the same or adjacent vertebrae of a patient's spine through individual percutaneous incisions corresponding to the pedicle screws. Fixation or fusion rods are then inserted into the body through one of those incisions, or through an additional incision adjacent to the most cephalad or caudal pedicle screw, and the rod is rigidly connected to the pedicle screws such that the rod extends along the longitudinal axis of the spine (i.e., along the cephalad/caudal direction) in order to fix the relative positions of the adjacent vertebrae to which the rod is connected. In some such minimally invasive procedures, a device (e.g., a cannula, tower, or portal) is connected to each of the pedicle screws and extends through the respective percutaneous incision. Moreover, it is known to utilize separate elongate blades connected with the screws. Such devices provide a percutaneous passageway through the tissue from each incision to the respective pedicle screw, in order to aid in the insertion of a spinal rod. Examples of such passageway devices are described in commonly-assigned U.S. Pat. No. 7,955,355 (“the '355 patent”) and U.S. Pat. No. 8,002,798 (“the '798 patent”), the entireties of which are hereby incorporated by reference herein as if fully set forth herein.
Often pedicle screw fixation constructs are used in conjunction with an interbody fusion technique, where the fixation constructs provide additional stability to the interbody fusion. Examples of interbody fusion techniques performed along a posterior approach include posterior lumbar interbody fusion (PLIF) and transforaminal lumbar interbody fusion (TLIF). Examples of interbody fusion techniques along other approaches to the spine include anterior lumbar interbody fusion (ALIF) and lateral interbody fusion. Typically, all of such interbody fusion techniques involve removing at least a portion of the intervertebral disc between two adjacent vertebral bodies and then positioning an interbody implant (such as a cage, which may be packed with bone graft material) into the intervertebral space created by the removal of the disc material.
Although considerable effort has been devoted in the art to optimization of such spinal fusion systems and techniques, still further improvement would be desirable.